In U.S. Pat. No. 4,434,247 issued Feb. 28, 1984, there is disclosed a process for producing methanol, ethanol and ethylene glycol from synthesis gas employing a homogeneous ruthenium catalyst, preferably with a Lewis base promoter. It is always desired to improve such processes to achieve higher reaction rates and further selectivity of the final product.
Others have previously attempted to improve the activity or selectivity of homogeneous ruthenium catalysts for alcohol production by the addition of various promoters or co-catalysts. For example, in U.S. Pat. No. 4,332,914 issued June 1, 1982 it is said that halogen-free rhenium or manganese compounds added to a ruthenium catalyst dispersed in a low-melting quaternary phosphonium base or salt serve to increase the selectivity to methanol. In U.S. Pat. No. 4,332,914, issued June 1, 1982 it is said that the presence of a cobalt compound in a similar ruthenium catalyst system improves the selectivity to ethanol. It is further alleged in U.S. Pat. No. 4,339,545 issued June 13, 1983, that the addition of halogen-free titanium or zirconium compounds to a ruthenium catalyst in a low-melting quaternary phosphonium or ammonium base or salt increases the selectivity toward ethanol. In U.S. Pat. No. 4,436,837 issued Mar. 13, 1984 it is noted that a combination of a ruthenium compound, a samarium compound, a quaternary phosphonium salt, and an inert oxygenated solvent provides a catalytic system with improved selectivity to ethanol.
In none of these patents however is it said or shown that the total activity (total yield of methanol, ethanol and other organic products) can be increased by the added metal complex. Indeed, where direct comparisons are possible, as in U.S. Pat. No. 4,436,837, it is apparent that the total activity has been lowered by the added metal complex. The effect of the additional metal complex is apparently only to change the product distribution, not the rate of total product formation.
Lanthanides were said to be useful as co-catalysts with nickel and a halogen promoter in the carbonylation of an alcohol to its corresponding carboxylic acid in U.S. Pat. No. 4,426,537, issued Jan. 17, 1984. Other catalyst systems employing a lanthanide and aluminum are disclosed in U.S. Pat. No. 3,867,312 issued Feb. 18, 1975 and U.S. Pat. No. 4,429,089 issued Jan. 31, 1984. In none of such catalyst systems were lanthanides employed with ruthenium, nor were alkanols prepared from synthesis gas.
It is, accordingly, desired to increase the activity and/or selectivity of the homogeneous catalysts based upon ruthenium to convert synthesis gas to the desired alcohols at higher rates and with the capacity to selectively produce higher proportions methanol or ethanol and lower proportions of ethylene glycol.